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Fuzzy logic provides a natural way of dealing with models that require the modeler or user to interpret linguistic variables in order to make a decision. This study focuses on employing fuzzy logic methodologies in order to create an Alamo switchgrass ecological site suitability map for the state of Mississippi. The inputs in the model are available water content (AWC), slope, pH, drainage, color, and texture. All variables were examined through the fist six inches (15cm) of soil. These six variables were assigned fuzzy restrictions based on expert knowledge from plant and soil scientists, combined using the fuzzy additive weighting method, then defuzzified using the center of gravity approach. The result of the final model is a switchgrass ecological site suitability model that uses expert knowledge and classifies sites into five linguistic categories.

This thesis summarizes an investigation into the need for removing extractives from herbaceous biomass feedstocks prior to their chemical characterization. Switchgrass (Panicum virgatum), was used in this study as a representative herbaceous biomass feedstock. The influence of extractives on the chemical analysis of switchgrass was done by comparing the composition of native switchgrass and solvent-extracted switchgrass preparations. Solvent-extracted switchgrass was prepared by extracting the native feedstock with either 95% ethanol, hot water or sequentially with ethanol and then water. Each of the feedstocks was analyzed for glycans, Klason lignin, acid soluble lignin, protein, ash, acetic acid and uronic acids. The results demonstrate that the extractives in native switchgrass significantly interfere with the analysis of Klason lignin. The lignin content of the feedstock was overestimated if the extractives were not removed prior to the analysis. The extractives in switchgrass did not affect glycan analyses. However, some soluble sugars are removed from the feedstock during the solvent extraction process. Total extractives removed by ethanol, water and ethanol/water amounted to 9.74%, 16.42%, and 19.11% of the feedstocks total solids, respectively. These amounts of extractives increased Klason lignin values by 4%, 4.5%, and 6.5% (on a wt percent of total solids), respectively. Most of the extractives in switchgrass are water-soluble and approximately one-quarter of these extractives measure as Klason Lignin. The removal of the water soluble extractives from the feedstock improved the mass closure values for the feedstock's summative analysis. Successive ethanol and hot water extraction has successfully removed most of the extractives in switchgrass yielding 100.4% mass balance. The recommended approach for the analysis of herbaceous biomass feedstocks will include sequential 95% ethanol and hot water extraction followed by chemical analysis on both the preextracted substrate and the extractives obtained from that substrate. / Graduation date: 1996

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Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 161-175).

Made available in DSpace on 2016-08-29T15:38:11Z (GMT). No. of bitstreams: 1 tese_6301_Dissertação Thiago Final.pdf: 5267139 bytes, checksum: 4ee972c2529c78fe446c30884eda190c (MD5) Previous issue date: 2013-02-25 / As pastagens representam a base da alimentação dos bovinos no Brasil, que em sua maioria, são manejados em pastagens extensivas. Porém, limitações nutricionais, em especial do nitrogênio, contribuem para a baixa produção de forragem nas áreas manejadas. O objetivo deste trabalho foi avaliar o efeito da aplicação de fontes e doses de nitrogênio nos atributos químicos do solo, no desenvolvimento e extração de nutrientes do capim-mombaça. O experimento foi desenvolvido entre outubro de 2011 e abril de 2012, no Instituto Federal do Espírito Santo campus Santa Teresa. Foi utilizada uma pastagem já estabelecida, onde cada parcela ocupou uma área de 6 m2. O delineamento experimental utilizado foi em blocos casualizados, com três repetições, em esquema fatorial 3 x 6, sendo três fertilizantes nitrogenados (uréia, sulfato de amônio e nitrato de cálcio) e seis doses de nitrogênio (0, 120, 240, 360, 480, 600 kg N ha-1), aplicados durante o período experimental, totalizando 54 unidades experimentais. As doses de nitrogênio foram divididas em sete aplicações, sendo os tratamentos aplicados a cada 28 dias, sempre após o corte da forrageira, totalizando sete cortes durante o período experimental de 196 dias. Em cada corte, a planta forrageira foi coletada com auxílio de um quadrado de ferro de 50 x 50 cm e cortada com tesoura de aço. O material coletado em cada parcela foi levado à estufa com circulação de ar, para determinação da matéria pré-seca. Após a secagem, as amostras foram moídas para determinação da matéria seca. O material moído foi encaminhado para o laboratório para avaliação dos teores dos macronutrientes no tecido vegetal e esses resultados foram utilizados na quantificação da extração de nutrientes pela forrageira. Foi ainda, ao final do experimento, coletadas com o auxílio de um trado, amostras de solo na profundidade de 0-20 e 20-40 cm, para avaliar o efeito da aplicação dos tratamentos sobre os atributos químicos do solo nas diferentes profundidades. Referente à produção de forragem, os resultados mostram que o capim-mombaça é responsivo à adubação nitrogenada e sua resposta em produção de matéria seca e número de perfilhos para uma mesma dose de nitrogênio varia em função da fonte utilizada. Os melhores resultados para as variáveis avaliadas foram obtidos com o uso do nitrato de cálcio como fonte de nitrogênio. Os resultados das análises de solo demonstraram que o sulfato de amônio apresentou elevado potencial de acidificação do solo. A redução provocada no pH do solo resultou em alterações nos teores de alumínio trocável, acidez potencial e na disponibilidade de fósforo no solo. Além disso, a aplicação de elevadas doses de nitrogênio na forma de sulfato de amônio e nitrato de cálcio, promoveu a lixiviação de bases, especialmente do potássio, para a camada de 20-40 cm. Palavras-chave: Panicum maximum, fertilizantes nitrogenados, matéria seca, acidez do solo.

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The dormancy of switchgrass (Panicum virgatum L.) seeds may be broken by a variety of treatments, including after-ripening and stratification. This study was conducted to investigate and characterize more systematically factors affecting both after-ripening and stratification effectiveness, and the aging that can occur concomitantly with after-ripening. More than one year of after-ripening at ambient temperature and humidity was necessary for germination of newly harvested seeds to increase from as low as 5% to around 80%. After-ripening was not accelerated at temperatures above ambient for seeds stored in paper bags, which permitted the loss of seed moisture at the increased temperatures. Both after-ripening and aging accelerated with increases in temperature (5 to 60°C) and seed moisture content (50 to 130 g kg⁻¹), except that there was evidence of a moisture optimum for after-ripening that shifted downward as temperature increased. For many seedlots, storage at 60°C and 50 g kg⁻¹ seed moisture content for about 1 mo broke most of the dormancy and resulted in acceptably low numbers of abnormal (aged) seedlings. Decreases in germinability caused by post-stratification drying of switchgrass seeds (described herein as "reversion", in which the reverted seeds could be made germinable again by further stratification) increased as the desiccation increased. Revertibility decreased as stratification or after-ripening time increased. Stratification and after-ripening worked additively to release switchgrass seeds from dormancy. Reversion (germination with stratification minus germination after stratification followed by drying) may reveal seedlot differences and changes over time and moisture content that can not be seen otherwise. Imbibed, dormant seeds placed at 21 or 30°C were induced into deeper dormancy, as indicated by length of stratification needed to break the dormancy. Dormancy deepened more as storage temperature and time increased for imbibed seeds. There are transitional temperature and seed moisture ranges where opposing processes (aging vs. after-ripening, stratification vs. dormancy deepening) appeared to overlap or surpass one another. Switchgrass seeds, either on a single seed level, or on the population level, responded continuously to changing temperature and moisture conditions. Less aging was observed for switchgrass seeds stored in N₂. After-ripening of switchgrass seemed not to be influenced by N₂ or air. In sum, switchgrass is revealed to be remarkably plastic in its ability to move toward both greater germinability and greater dormancy. / Ph. D.

Switchgrass (Panicum virgatum L.), a warm-season grass, grows most rapidly in mid-summer when cool-season species such as tall fescue (Festuca arundinacea Schreb.) may have limited growth due to high temperature and low soil moisture availability. The objectives of this study were to investigate physiological factors and to determine management strategies that could optimize growth of switchgrass. The influences of two successive drought cycles on performance and water relation parameters of switchgrass and tall fescue were studied in growth chamber conditions. Water was withheld from conditioned plants until elongation of tillers stopped. Then pots were rewatered and a new drought cycle followed. Control plants remained well watered during this time. Both conditioned and control plants were then subjected to a challenge water stress. Total leaf elongation and soil water content (SWC) were measured daily. Leaf water potential (Ψ), osmotic potential (Π), relative water content, and concentrations of K, Na, Ca, and total free sugars were measured at the end of each water-stress cycle. Osmotic potential at full turgor (Π₁₀₀), symplastic water content (SYM) , and modulus of elasticity (∊) were determined from pressure-volume curves at the end of the two conditioning cycles. Conditioned plants of both species elongated more during the challenge water-stress than control plants and had lower SWC and Ψ when their leaf elongation ceased. Conditioned plants exhibited osmotic adjustment, accumulating free sugars and K, as a result of drought stress. Switchgrass SYM did not change, while Π₁₀₀ decreased, suggesting active salt accumulation. Increased ∊ somewhat counteracted the beneficial influence of osmotic adjustment. Tall fescue SYM increased, while Π₁₀₀ did not change. Decreased ∊ improved drought tolerance of tall fescue. Field experiments were conducted to investigate the influence of date of first harvest and cutting height on yield distribution and canopy characteristics of ‘Pathfinder’ (2-yr study), ‘Cave-in-rock’, and ‘Blackwell’ (1-yr study) switchgrass. Seasonal distribution of dry matter production was established by measuring first-harvest yields and regrowth. The canopy of Pathfinder was characterized by determining number and weight of tillers, light penetration, leafiness, specific leaf weight, and leaf area index in profiles of the canopy before harvest and in regrowth. First-harvest yields increased as date of first cut was delayed and cutting height was lowered. Cutting at 20 cm decreased the yield of first cutting in a second growing season. Plots not harvested in the first growing season gave higher yields in the second growing season compared with previously harvested plots, suggesting that any harvest may decrease subsequent yield potential. Regrowth decreased as date of first cut was delayed. A cutting height of 30 cm produced greater regrowth than cutting at 20 cm. Yields and canopy characteristics suggest that removal of growing points decreased second-harvest yields and weakened regrowth potential in the following year. To maximize regrowth to be used for grazing during July and August, switchgrass hay should be cut after 10 June and before 21 June. / Ph. D.